A Quantitative Model for Human Olfactory Receptors

A wide variety of chemicals having distinct odors are smelled by humans. Odor perception initiates in the nose, where it is detected by a large family of olfactory receptors (ORs). Based on divergence of evolutionary model, a sequence of human ORs database has been proposed by D. Lancet et al (2000, 2006). It is quite impossible to infer whether a given sequence of nucleotides is a human OR or not, without any biological experimental validation. In our perspective, a proper quantitative understanding of these ORs is required to justify or nullify whether a given sequence is a human OR or not. In this paper, all human OR sequences have been quantified, and a set of clusters have been made using the quantitative results based on two different metrics. Using this proposed quantitative model, one can easily make probable justification or deterministic nullification whether a given sequence of nucleotides is a probable human OR homologue or not, without seeking any biological experiment. Of course a further biological experiment is essential to validate the probable human OR homologue

Graphite-Fiber Elastic Constants: Determination from Ultrasonic Measurements on Composite Materials

We determined the complete five-component transverse-isotropic-symmetry elastic-constant tensor for two graphite fibers: high-strength/low-modulus and low-strength/high-modulus. We did this in two steps. First, we measured ultrasonically the complete elastic constants of a metal matrix with embedded uniaxial graphite fibers. Second, we did an inverse—modeling calculation to extract the fiber’s elastic constants. This calculation requires three inputs: composite elastic constants, matrix elastic constants, and fiber-matrix phase geometry, principally the fiber volume fraction. We compare the results with those expected for a random quasiisotropic graphite aggregate and for a hypothetical graphite fiber with perfectly aligned basal planes

Long-range temporal correlations in scale-free neuromorphic networks

© 2020 Massachusetts Institute of Technology. Biological neuronal networks are the computing engines of the mammalian brain. These networks exhibit structural characteristics such as hierarchical architectures, small-world attributes, and scale-free topologies, providing the basis for the emergence of rich temporal characteristics such as scale-free dynamics and long-range temporal correlations. Devices that have both the topological and the temporal features of a neuronal network would be a significant step toward constructing a neuromorphic system that can emulate the computational ability and energy efficiency of the human brain. Here we use numerical simulations to show that percolating networks of nanoparticles exhibit structural properties that are reminiscent of biological neuronal networks, and then show experimentally that stimulation of percolating networks by an external voltage stimulus produces temporal dynamics that are self-similar, follow power-law scaling, and exhibit long-range temporal correlations. These results are expected to have important implications for the development of neuromorphic devices, especially for those based on the concept of reservoir computing

In vivo Evaluation Of Antidiarrhoeal Activity Of Rhus semialata Fruit Extract In Rats

Rhus semialata Murr. (Anacardiaceae) is a deciduous tree of north eastern India. The fruit of this plant is traditionally used to control diarrhoea and dysentery. The Present study was undertaken to evaluate anti-diarrhoeal potency of methanol extract of fruits of Rhus semialata using Wister albino rats to substantiate folklore claims. The extract at graded doses (100, 200, 400 and 600 mg/kg body weight) was investigated for anti-diarrhoeal activity in term of reduction in the rate of defecation in castor oil induced diarrhoea. To understand the mechanism of its antidiarrhoeal activity, the gastrointestinal transit and PGE2-induced intestinal fluid accumulation (enteropooling) were further evaluated. At graded doses, the extract showed a remarkable anti-diarrhoeal activity evidenced by the reduction in the rate of defecation up to 80.70 % of control diarrhoeal animals at the dose of 600 mg/kg body weight. Results are comparable to that of standard drug diphenoxylate (50 mg/kg body weight). Extract produced profound decrease in intestinal transit (8.02 – 47.05 %) at selected doses comparable to that of single intraperitoneal injection of standard drug atropine sulphate at doses of 0.1 mg/kg body weight. It significantly inhibited PGE2 - induced enteropooling (21.98 – 56.03 %). The results indicated that the methanol extract of the fruits of R. semialata possesses significant anti-diarrhoeal effect and substantiated the use of this herbal remedy as a non-specific treatment for diarrhoea in folk medicine. Keywords: Atropin sulphate, Castor oil, Diarrhoea, Diphenoxylate, Rhus semialata. African Journal of Traditional and Complementary Medicine Vol. 5 (1) 2008: pp. 97-10

Atomic Scale Dynamics Drive Brain-like Avalanches in Percolating Nanostructured Networks.

Self-assembled networks of nanoparticles and nanowires have recently emerged as promising systems for brain-like computation. Here, we focus on percolating networks of nanoparticles which exhibit brain-like dynamics. We use a combination of experiments and simulations to show that the brain-like network dynamics emerge from atomic-scale switching dynamics inside tunnel gaps that are distributed throughout the network. The atomic-scale dynamics emulate leaky integrate and fire (LIF) mechanisms in biological neurons, leading to the generation of critical avalanches of signals. These avalanches are quantitatively the same as those observed in cortical tissue and are signatures of the correlations that are required for computation. We show that the avalanches are associated with dynamical restructuring of the networks which self-tune to balanced states consistent with self-organized criticality. Our simulations allow visualization of the network states and detailed mechanisms of signal propagation

Interface Effects on Attenuation and Phase Velocities in Metal-Matrix Composites

One often determines the effective elastic moduli and damping of a heterogeneous material by using elastic waves (propagating or standing). Several theoretical studies show that for long wavelengths one can calculate the effective wave speeds of plane longitudinal and shear waves through a composite material. At long wavelengths the wave speeds thus calculated are nondispersive and hence provide the values for the static effective elastic properties. References to some of the recent theoretical and experimental studies can be found in [1–12]. The scattering formulations developed in [1–8] provide a means to obtain both the effective wave speeds and the damping caused by scattering

Synaptic dynamics in complex self-assembled nanoparticle networks.

We report a detailed study of neuromorphic switching behaviour in inherently complex percolating networks of self-assembled metal nanoparticles. We show that variation of the strength and duration of the electric field applied to this network of synapse-like atomic switches allows us to control the switching dynamics. Switching is observed for voltages above a well-defined threshold, with higher voltages leading to increased switching rates. We demonstrate two behavioral archetypes and show how the switching dynamics change as a function of duration and amplitude of the voltage stimulus. We show that the state of each synapse can influence the activity of the other synapses, leading to complex switching dynamics. We further demonstrate the influence of the morphology of the network on the measured device properties, and the constraints imposed by the overall network conductance. The correlated switching dynamics, device stability over long periods, and the simplicity of the device fabrication provide an attractive pathway to practical implementation of on-chip neuromorphic computing

Polyphenolic acetates: A newer anti-Mycobacterial therapeutic option

The objective of our research project was screening of various highly specific substrates of Acetoxy Drug: Protein Transacytylase (M.TAase) for antimycobacterial activity. Mycobacterial culture was done in Middlebrook’s 7H9 media. Protein purification (Mycobacterial Tranacetylase, M.TAase) was done by ion exchange chromatography and its demonstration was done on SDS- polyacrylamide gel electrophoresis (SDS-PAGE) and western blot. Middlebrook’s 7H9 broth was procured from Becton Dickinson. CM-Sepharose, DEAE-Sepharose and Q-Sephharose were purchased from Amersham Pharmacia. Anti acetyl lysine polyclonal antibody was purchased from Cell Signaling. The Middlebrook 7H9 medium was used for M. smegmatis culture. The media was prepared according to the manufacturer’s instructions. The various Polyphenol acetate compounds were tested for their antimycobacterial activities. Minimal inhibitory concentrations (MIC) were calculated by Alamar blue dye assay method. The GST protein was used as a receptor protein and purified Mycobacterial Glutamine Synthetase (GS) as TAase for acetylation by DAMC. To demonstrate the TAase catalyzed acetylation of GST by DAMC, purified M.TAase (GS) was preincubated with GST and DAMC followed by western blot using anti acetyl lysine antibody, which avidly react with the acetylated proteins. The growth pattern of M. smegmatis was diminished under the influence of various polyphenolic acetates (PA) tested for their anti-mycobacterial activity. DAMC and DAMC-5-carboxylic acid was found to have MIC of 40μg/ml whereas DAMC-6-carboxylic acid was reported to have MIC value of 35μg/ml and for ellagic acid tetra acetate (EATA) it was 60μg/ml. Previous work in our lab has led to discovery of a novel enzyme acetoxy drug: protein transacetylase (TAase), catalyzing transfer of acetyl group from various polyphenolic peracetate (PA) to certain receptor proteins such as cytochromes P-450, NADPH cytochrome reductase, nitric oxide synthase (NOS) has been established in various eukaryotic as well as prokaryotic sources. PA(s) irreversible inhibitors of mammalian CYP linked MFO, possibly due to modification of cytochrome p- 450 by acetylation in a reaction catalysed by M.TAase (GS) utilizing PA(s) as a donor of acetyl groups. Accordingly, it was hypothesized that the CYP51 of mycobacteria involved in the cell wall sterol synthesis could possibly be modified by our PA(s) through the novel unknown action of GS as transacetylase leading to the death of mycobacterial cell by way of acetylation catalyzed by acetoxy drug: protein transacetylase (M.TAase or GS).Keywords: Transacetylase; Glutamine synthetase; Mycobacterium smegmatis; Polyphenolic acetates; Acetoxy drug: protein transacetylas